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<title>Problem 1645. -- [Usaco2007 Open]City Horizon -- 衡阳八中OJ离线版-2012-02-29</title><center><h2>1645: [Usaco2007 Open]City Horizon</h2><span class=green>Time Limit: </span>5 Sec&nbsp;&nbsp;<span class=green>Memory Limit: </span>64 MB<br><span class=green>Submit: </span>122&nbsp;&nbsp;<span class=green>Solved: </span>63<br>[<a href='submitpage.php?id=1645'>Submit</a>][<a href='problemstatus.php?id=1645'>Status</a>][<a href='bbs.php?id=1645'>Discuss</a>]</center><h2>Description</h2><div class=content>Farmer John has taken his cows on a trip to the city! As the sun
sets, the cows gaze at the city horizon and observe the beautiful
silhouettes formed by the rectangular buildings.

The entire horizon is represented by a number line with N (1 <= N
<= 40,000) buildings. Building i's silhouette has a base that spans
locations A_i through B_i along the horizon (1 <= A_i < B_i <=
1,000,000,000) and has height H_i (1 <= H_i <= 1,000,000,000).
Determine the area, in square units, of the aggregate silhouette
formed by all N buildings.

N个矩形块，交求面积并.</div><h2>Input</h2><div class=content>* Line 1: A single integer: N

* Lines 2..N+1: Input line i+1 describes building i with three
        space-separated integers: A_i, B_i, and H_i

</div><h2>Output</h2><div class=content>* Line 1: The total area, in square units, of the silhouettes formed
        by all N buildings

</div><h2>Sample Input</h2>
			<div class=content><span class=sampledata>4<br />
2 5 1<br />
9 10 4<br />
6 8 2<br />
4 6 3<br />
</span></div><h2>Sample Output</h2>
			<div class=content><span class=sampledata>16<br />
<br />
OUTPUT DETAILS:<br />
<br />
The first building overlaps with the fourth building for an area of 1<br />
square unit, so the total area is just 3*1 + 1*4 + 2*2 + 2*3 - 1 = 16.</span></div><h2>HINT</h2>
			<div class=content><p></p></div><h2>Source</h2>
			<div class=content><p><a href='problemset.html?search=Silver'>Silver</a></p></div><center>[<a href='submitpage.php?id=1645'>Submit</a>][<a href='problemstatus.php?id=1645'>Status</a>][<a href='bbs.php?id=1645'>Discuss</a>]</center>﻿<br>

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